Lithium secondary battery and non-aqueous electrolytic solution

Abstract

The sudden generation of heat being frequently caused in the case of the overcharge of a lithium secondary cell which have a positive electrode comprising a composite metal oxide of lithium and cobalt or a composite metal oxide of lithium and nickel, a negative electrode comprising metallic lithium, a lithium alloy or a material capable of occluding and releasing lithium, and a nonaqueous electrolyte solution comprising a nonaqueous solvent and an electrolyte dissolved therein can be efficiently prevented by the addition, to the nonaqueous electrolyte solution, of an organic compound which, when the lithium secondary cell is overcharged, decomposes into a decomposition product capable of dissolving out the cobalt or nickel contained in the positive electrode and depositing it ion the negative electrode (for example, a tert-alkylbenzene derivative).

1. A lithium secondary battery which comprises a positive electrode of a composite metal oxide comprising lithium and a metal selected from the group consisting of cobalt and nickel, a negative electrode comprising a lithium metal, a lithium alloy or a material capable occluding and releasing lithium, and a non-aqueous electrolyte solution comprising an electrolyte in a non-aqueous solvent, wherein the non-aqueous electrolyte solution contains 1 to 5 weight % of a combination of a tert-butylbenzene derivative and cyclohexylbenzene, wherein the tert-butylbenzene derivative is selected from the group consisting of tert-butylbenzene, 1-fluoro-4-tert-butylbenzene, 1-chloro-4-tert-butylbenzene, 1-bromo-4-tert-butylbenzene, 1-iodo-4-tert-butylbenzene, 5-tert-butyl-m-xylene, 4-tert-butyltoluene, 3,5-di-tert-butyltoluene, 1,3-di-tert-butylbenzene, 1,4-di-tert-butylbenzene, and 1,3,5-tri-tert-butylbenzene. 
     
     
       2. The lithium secondary battery of  claim 1 , wherein the tert-butylbenzene derivative is tert-butylbenzene or 1,3-di-tert-butyl-ibenzene. 
     
     
       3. The lithium secondary battery of  claim 1 , wherein the tert-butylbenzene derivative is contained in an amount of 0.3-3 parts, per one part of the cyclohexylbenzene. 
     
     
       4. The lithium secondary battery of  claim 1 , wherein the non-aqueous solvent comprises a combination of a cyclic carbonate and a linear carbonate. 
     
     
       5. The lithium secondary battery of  claim 1 , wherein the non-aqueous solvent contains a cyclic carbonate selected from the group consisting of ethylene carbonate, propylene carbonate, butylene carbonate and vinylene carbonate. 
     
     
       6. The lithium secondary battery of  claim 1 , wherein the non-aqueous solvent contains a linear carbonate selected from the group consisting of dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate. 
     
     
       7. The lithium secondary battery of  claim 1 , wherein the negative electrode is graphite. 
     
     
       8. The lithium secondary battery of  claim 1 , wherein the negative electrode is carbonaceous material having a graphite crystal structure in which a lattice distance of lattice surface (002) is in the range of 0.335 to 0.340 nm. 
     
     
       9. The lithium secondary battery of  claim 1 , wherein the non-aqueous solvent contains two or more cyclic carbonates.